Inspection methods for small bore pipes

ABSTRACT

A novel video inspection method for an interior surface of a small diameter pipe may include the steps of advancing a videoscope through the pipe of known size while acquiring raw images therefrom; estimating the video camera pose for at least some of the raw images; sequentially building a pipe point cloud, a mesh, and a 3D textured model of the interior surface of the pipe from the raw images with adjustments for video camera poses; unwrapping the raw images using camera poses and the pipe point cloud to create unwrapped images of the interior surface of the pipe; and creating a panoramic image of the interior surface of the pipe by stitching the unwrapped images together. The method improves on a conventional Structure-from-Motion technique and allows enhanced sharpness, reduced artifacts, and improved uniformity of lighting as a result of reduced model noise and removal of outliers. The method may be implemented with conventional video borescopes by postprocessing raw images using proprietary software.

CROSS-REFERENCE DATA

This US application is a continuation-in-part of the PCT Application No.WO2022172048 filed 15 Feb. 2021 with the same title, which isincorporated herein in its entirety by reference.

BACKGROUND

Without limiting the scope of the invention, its background is describedin connection with the non-destructive inspection of pipelines. Moreparticularly, the invention describes improved remote video inspectionmethods of image processing obtained using a conventional small-diametervideoscope to present to the observer an accurate unwrapped combinedimage of the internal surface of a small bore pipe.

The use of pipe networks is common in several industries, including oiland gas, petrochemical, nuclear, and aerospace as some examples. Regularnon-destructive examination and assessment of these pipes to ensure safeoperation is common and often required by safety regulations. Otherexamples of pipe networks that require inspection include water pipesand drain pipes. Optical cameras are frequently used where human accessis constrained—typically by hazardous conditions or small pipediameters.

Traditional systems and methods for inspecting the pipes may include avideo camera head mounted on a push-cable that is deployed along a pipeto display the interior pf the pipe on a camera control unit or anothervideo display. Such video camera heads are essential tools to visuallyinspect the interior of the pipes and to identify possible defectstherein, for example, pipe cracks or breaks, corrosion, leakage, and/orother defects or blockages inside the pipe. Traditional pipe inspectionsystems, though useful, are limited to manually performed visualinspection and interpretation of the images of pipes by an operator.Existing lateral push-cable camera systems generally include analogcameras with poor image quality due to limitations in power and signalprocessing down a lengthy push-cable, where the camera head must besufficiently small to fit into and navigate the bends and turns ofcommonly used pipe diameters.

The problem may be exacerbated further by a small diameter of the pipe,such as under 25 mm, as it may restrict the view of the camera andfurther limit the ability of the operator to identify possible defectstherein.

The need, therefore, exists for improved pipe inspection methods inorder to increase confidence in assessment results and more reliablyidentify problem areas inside a pipe network.

SUMMARY

Accordingly, it is an object of the present invention to overcome theseand other drawbacks of the prior art by providing novel methods forenhanced visual inspection of pipes, and in particular of small borepipelines and networks.

It is another object of the present invention to provide novel methodsfor remote visual inspection of pipes with improved image quality.

It is a further object of the present invention to provide novel methodsof visual inspection adapted to operate with existing visual inspectionequipment and yet provide improved image representation of interiorsurfaces of small bore pipes.

It is yet a further object of the present invention to provide improvedmethods for remote visual inspection using a small diameter handheldvideoscope equipped with just the video camera and without additionalsensors, laser projectors, pipe crawler mechanisms, or camerapositioning and centering hardware.

It is yet another object of the present invention to provide novelvisual inspection methods allowing to localize identified pipe defectswith greater accuracy along the length of the pipe.

It is a further yet object of the present invention to provide novelvisual inspection methods configured to compensate for the low lightintensity of the raw images acquired by the videoscope.

The novel video inspection method for an interior surface of a pipe ofthe present invention may include the conventional steps of (a) definingthe geometrical size and shape of the interior surface of the pipe, (b)providing a videoscope sized to fit inside the pipe, (c) advancing thevideoscope through the pipe while acquiring raw images from the videocamera of the videoscope. The method further includes the novel steps of(d) estimating the video camera pose for at least some of the raw imagesof step (c), (e) sequentially building a pipe point cloud, a mesh, and a3D textured model of the interior surface of the pipe from the rawimages with adjustments for video camera poses, (f) unwrapping the rawimages using corresponding video camera poses and the pipe point cloudto create unwrapped images of the interior surface of the pipe, and (g)creating a panoramic image of the interior surface of the pipe bystitching the unwrapped images together.

The step of extracting and matching unique features of the images may beperformed using pipe point clouds and Structure-from-Motion techniquesas a basis. Beyond that, the method of the invention allows enhancedsharpness, reduced artifacts, and improved uniformity of lighting as aresult of reduced model noise and removal of outliers as described ingreater detail below.

The method of the invention may be implemented in a software productconfigured to perform the steps of the method. The software may beloaded on a suitable computer, tablet, smartphone, or anotherappropriate electronic device.

BRIEF DESCRIPTION OF THE DRAWINGS

Subject matter is particularly pointed out and distinctly claimed in theconcluding portion of the specification. The foregoing and otherfeatures of the present disclosure will become more fully apparent fromthe following description and appended claims, taken in conjunction withthe accompanying drawings. Understanding that these drawings depict onlyseveral embodiments in accordance with the disclosure and are,therefore, not to be considered limiting of its scope, the disclosurewill be described with additional specificity and detail through the useof the accompanying drawings, in which:

FIG. 1 is a block diagram of the components of the system to implementthe present invention, listing major functional blocks thereof,

FIG. 2 is an example of point cloud and camera poses calculatedtherefore for an interior of a rectangular pipe,

FIG. 3 is an example of a reconstructed 3D model fitted to a pipe withknown geometry,

FIG. 4 illustrates the camera position and projected rays as part ofimage unwrapping,

FIG. 5 shows an example of projected rays fitted to the geometry of aninterior of a round pipe,

FIG. 6 shows an example of a raw image seen by a camera inside a roundpipe,

FIG. 7 shows a postprocessing step of fitting projected rays onto a rawimage from FIG. 6 ,

FIG. 8 is another example of a raw image seen by the camera inside around pipe,

FIG. 9 is an example of an unwrapped image from that of FIG. 8 ,

FIG. 10 is yet another example of a raw image from a camera positionedinside a round pipe,

FIG. 11 is an example of unwrapping of the image of FIG. 10 ,

FIG. 12 is an example of manual image stitching using a plurality ofunwrapped images,

FIG. 13 is an example of an unwrapped raw image of the internal surfaceof a round pipe,

FIG. 14 is an example of a weighted image of FIG. 13 to adjust thelighting thereof,

FIG. 15 is an illustration of using camera poses for automated imagestitching, and

FIGS. 16 a to 16 d show examples of using Structure-from-Motion andimage stitching to develop a smooth unwrapped image of the interiorsurface of the pipe.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The following description sets forth various examples along withspecific details to provide a thorough understanding of claimed subjectmatter. It will be understood by those skilled in the art, however, thatclaimed subject matter may be practiced without one or more of thespecific details disclosed herein. Further, in some circumstances,well-known methods, procedures, systems, components and/or circuits havenot been described in detail in order to avoid unnecessarily obscuringclaimed subject matter. In the following detailed description, referenceis made to the accompanying drawings, which form a part hereof. In thedrawings, similar symbols typically identify similar components, unlesscontext dictates otherwise. The illustrative embodiments described inthe detailed description, drawings, and claims are not meant to belimiting. Other embodiments may be utilized, and other changes may bemade, without departing from the spirit or scope of the subject matterpresented here. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe figures, can be arranged, substituted, combined, and designed in awide variety of different configurations, all of which are explicitlycontemplated and make part of this disclosure.

While the present invention may be useful for video inspection of avariety of internal surfaces of pipes, containers, canisters,reservoirs, and other cavities, it has a particularly advantageousutility in inspecting small-diameter pipes, such as 25 mm or smaller.This is because it only uses a feed of video or still images provided bya camera at the end of the scope, which may be obtained with additionallighting from an array of small-size LEDs. No other sensor, probe, orother hardware is required for applying the method of the invention,which makes the scope size as small as practical given the size of thesuitable camera and light source.

FIG. 1 illustrates a general block diagram of the main components of thesystem implementing the present invention. A conventional videoscope 10(shown in a dashed line) may include a handheld controller 12 with aflexible scope cable extending therefrom. A miniature camera 14 and alight source 16 (for example, an array of LEDs) may be mounted at theend of the flexible scope cable. The entire videoscope may be configuredto provide raw video and still images as the scope is advancedthroughout the internal space of a pipe under inspection.

Examples of suitable, commercially available videoscopes may include anOlympus IPLEX series of videoscopes (Olympus Corporation, Tokyo, Japan),which are only 2.4 mm in diameter, as well as a GE Video Borescope(General Electric, Boston, MA). Recent videoscope advances have producedeven smaller size videoscope, such as only 1 mm in diameter, forexample, a Super-ultra small industrial video borescope H NL-0.95CAM120by SPI Engineering (Nagano, Japan), which is only 0.95 mm in diameter.Such small videoscopes are appropriate for evaluating pipes of smalleryet diameters, such as sub-millimeter pipes, using the methods of thepresent invention.

While commercially available videoscopes feature a small built-indisplay for directly observing the images supplied by the video camera,at least some also feature an option to store collected images using aninternal or an external media storage element 20. Examples of a mediastorage element may include any suitable removable or embedded computermemory devices such as memory cards, sticks, tapes, etc., as the presentinvention is not limited in this regard. A further example of a mediastorage device 20 may include a plug-in cable configured to transmit thevideo images from the handheld videoscope 10 to any external computer30, which itself may include a media storage element 20 built-in orremovably attached thereto.

The method of the invention may be used to post-process the imagesobtained using the video camera either simultaneously with the processof advancing the videoscope along the pipe or at a later time using therecorded plurality of images, as the invention is not limited in thisregard.

In either case, novel methods of the invention may be implemented assoftware loaded on a suitable electronic device 30 directly attached toor otherwise capable of receiving the successive images of the internalsurface of the pipe from the videoscope 10, for example, via a memorystick file transfer. Examples of such suitable electronic computerdevices 30 capable of operating the software to implement the methods ofthe invention may include a personal computer, a smartphone, a tablet, alaptop, a smartwatch, etc., as the present invention is not limited inthis regard. In further embodiments of the invention, the images fromthe video camera 14 may be transmitted remotely (such as via theInternet) to a central server, which in this case may be configured topost-process the images, generate an unwrapped final result image andthen transmit it back to the user or store in memory for subsequentreview and further analysis. In this case, a suitable user interface,such as a suitable website configured for uploading the images to acentral server, may be provided as part of the system of the presentinvention. Such remote post-processing of images is included in thescope of the notion of the computer 30 and post-processing unit 40, asillustrated in FIG. 1 .

The post-processing unit 40 may include the following functional blocks:video camera pose estimation block 42, image unwrapping block 44, lightadjustment block 46, and image stitching block 48, all of which aredescribed below in greater detail. While in some embodiments, one ormore of these blocks may be implemented as physically stand-alone units,in other embodiments, they may be implemented as elements of a singlecomputer software product. In further yet embodiments of the invention,at least some of these functional blocks may be implemented as separatesoftware programs configured to operate with each other or with othercommercially available image-processing software products.

The output of the results of the post-processing transformation of theraw images obtained from the video camera 14 may be displayed for theobserver in a functional block 50, which may be implemented as acomputer monitor showing one or more of the unwrapped stitched images ofthe pipe interior surface. Alternatively, or in addition to a visualdisplay, the results may be presented to the observer as a print-out orin other suitable graphically observable ways.

According to the present invention, a video inspection of an interiorsurface of a pipe may start with a step of defining the geometrical sizeand shape of the interior surface of the pipe. This may be accomplishedby examining the pipe itself it is accessible or by inspecting therecords of the pipe collected during its construction. The internalsurface of the pipe may be defined as a 3D geometrical coordinate recordof the axis of the pipe combined with a record of its cross-sectionalarea. Accurate knowledge of the interior geometry of the pipe, in someembodiments exceeding a sub-millimeter accuracy, may be instrumental inthe proper fitting of the raw images obtained by the video camera to theactual dimensions defining the interior surface, as will be explainedbelow in greater detail. A mathematical (or virtual) model of theinterior surface of the pipe may then be created in order to define theboundaries of the surface, which naturally limits the field of view ofthe video camera during a pipe inspection.

Either before or after the step of obtaining the geometrical dimensionsof the pipe interior surface, the actual video inspection may be carriedout. It may include providing a videoscope equipped with a camera and alight source sized to fit inside the pipe. Advancing of the videoscopemay be conducted while acquiring raw images from the video camera asdiscussed above. An optional step of observing the video feed from thecamera may be instrumental in assuring the proper advancement of thevideoscope and in identifying any gross defects of the pipe.

Once the record of a plurality of the raw images is obtained, a seriesof steps of the post-processing part of the process may be initiated. Asa first step, a first, or preliminary determination of camera poses andpoint cloud may be created using a variety of techniques. One suitabletechnique for post-processing of the raw images is calledStructure-from-Motion, or SfM. Generally speaking, SfM techniqueinvolves the recognition and extraction of unique features of successiveimages so that the geometrical relationship of successive images can bedetermined in the relationship of one image to the next. SfM techniqueallows the reconstruction of a 3D image from a series of 2D imagesrecorded in a known succession.

As can be appreciated by those skilled in the art, the accuracy of thereconstructed 3D model highly depends on the quality of available 2Dimages. Low light intensity, for example, can reduce image quality,which may cause a reduction in the number of unique features availablefor reconstructing the 3D model. While videoscopes are equipped with anLED light source, such LEDs may not be able to completely cover thefield of view of the camera or not provide bright enough illumination ofthe pipe interior. These factors tend to introduce errors during the 3Dreconstruction process and texture rendering, making the final resultless than optimal for detecting pipe defects.

FIG. 2 shows an example of a first, or preliminary 3D reconstruction ofa rectangular pipe using a point cloud (shown as a plurality of rawpoints with varying density) and camera poses 15, as better seen in acircular zoom-in insert on the right of FIG. 2 . An assumption is madethat all images are captured by the same camera so the camera pose maybe extracted from the images by matching these unique features betweenvarious raw images.

Each point is shown in varying degrees of black, with less colorindicating fewer features extracted from the raw images, typicallybecause of the blurs or low light density. As can be observed, the pointcloud in this example contains many outliers, empty zones,discontinuities, and considerable noise, all of which may negativelyimpact the final result. Artificial discontinuities, for example, maycreate an impression of a defect in a place where there is no physicaldefect present. That may create a need for an unnecessary interventionand costly unnecessary repair.

To improve on this preliminary 3D reconstruction, the present inventioncontemplates an additional step of fitting the preliminary first 3Dreconstruction to a virtual model of a pipe created from the known pipegeometry and shape. In embodiments, the point cloud may be separatedinto individual slices in order to accommodate pipe bends and othercomplex geometry. The fitting procedure may be carried out by tuning theposes of the camera and fitted pipe slices, for example, with the goalof minimizing the average of the Euclidean distance between the fittedpipe and the corresponding preliminary point cloud slice. Using avirtual pipe model, the point cloud slices may be adjusted so as to fitthe virtual pipe as a whole, as seen in FIG. 3 , representing a secondpipe point cloud. This step may be instrumental in reducing the noise ofthe images and compensating for empty or dark regions of the pipe, ascan be appreciated from the description below.

Using a 3D textured model built as a result of implementing the stepsdescribed above, a step of image unwrapping may then be conducted. Imageunwrapping is a term generally describing a projection of the points inthe world coordinate to a 2D Cartesian coordinate. In this instance, aprojection of the 3D textured model onto a 2D surface is conducted inorder to create a final result of the inspection to be presented to theobserver of the test.

One advantageous technique for inspection images unwrapping for thepurposes of the present invention is depth-image-based-rendering and raytracing. The unwrapping step may be initiated by creating an unwrappedimage with multiple rays, as seen in FIG. 4 . Shown in FIG. 4 is anexample of a round pipe with a camera positioned along its central axis(after adjusting for camera poses as explained above based on the pointcloud and initial camera pose) and a plurality of rays oriented acrossthe pipe projected in front of the camera. These rays are projected ontoa virtual model of the round pipe, as seen in FIG. 5 . The correlatedpoints of the rays may then be projected onto the raw 2D images, forexample, see an image shown in FIG. 6 to create an image with rayprojections as seen in FIG. 7 .

A further advantageous step of the present invention includes lightingadjustment of the raw images, which can be carried out during the stepof image unwrapping. Low light intensity and the nature of a small-sizevideo camera may result in at least some portion of the acquired imagescontaining blurry areas and distortions. Mixing these “featureless”parts with other sharper and more detailed parts of the image may reducethe quality and sharpness of the final result. The methods of thepresent invention use a weight factor assigned to at least some or evenevery pixel on each image in order to reduce the contribution ofunfocused pixels and increase the contribution of pixels with high focusand sharpness.

In one example seen in FIG. 8 , the raw image has points with maximumcontribution close to the center of the image, while peripheral parts ofthe image have lower sharpness and therefore are assigned lower weightfactors. A linear increase of sharpness from the periphery towards thecenter of the image may be assumed, and therefore, a correspondinglinear increase in weight factors may be implemented before unwrappingthe image. FIG. 9 shows an example of using weight factors in unwrappingthe image of FIG. 8 . A lower contribution is represented by highertransparency, up to the point of abandoning some of the image parts atthe lower edge of the image. Abandoned parts of the image may becompensated by more sharp images of the same portion of the pipeobtained from other raw images so that blending of focused and unfocusedpixels of the same portion of the image is avoided—resulting in anincreased focus of the final result.

Another example of such image adjustment is seen in FIGS. 10 and 11 .FIG. 10 shows the raw image of the pipe interior, while FIG. 11 shows anadjusted unwrapped image of the same, created using FIG. 10 as astarting point.

Image stitching to create a panoramic combined image of the interiorsurface of the pipe may be the next step in the method of the invention.Traditionally, manually-conducted image stitching is a time-consumingprocess when it comes to consolidating a large number of images, whichcan easily go into hundreds or more images. In addition, variablelighting conditions may occur when different adjacent images are taken,due to movement of the video camera, light source repositioning, blindspots in illumination, and for other reasons. Variability in lightingmay cause the occurrence of light artifacts in the final panoramicimage, as can be seen in FIG. 12 , for example. Abrupt transitionsbetween well-lit and poorly lit areas of the pipe may create anerroneous impression of a presence of a defect in the pipe, which maynot be there.

The present invention addresses this problem by deploying a step ofadjusting image brightness for at least some of the images of the pipe,as illustrated in FIGS. 13 and 14 . FIG. 13 shows an example of a rawunwrapped image. The brightness of the image is a function of lighting,which is generally diminished from the center of the video camera (whichis located generally at the same spot as the light source) towards theperiphery of the image. Each image may be processed based on this oranother suitable light distribution model. In one example, the videocamera pose is estimated on the image, and a gradual decrease ofbrightness away from that point on the image is used to assignrespective weight factors to at least some or all pixels of the image.The lower weight factor results in a more transparent result of theweighted image—as seen in FIG. 14 around the edges of the image.

Processing of at least some or all of the images for adjustment of thebrightness before image stitching results in a more gradual finalpanoramic picture, thereby avoiding lighting artifacts and reducing thelikelihood of identifying a false defect in the pipe—as seen from theexamples described below.

FIG. 15 shows estimated poses of the video camera extracted from thepoint cloud during video inspection of a round pipe long a U-shapedcurve of the pipe position. Successive points indicate individual cameraposes when the images of the interior surface of the pipe were taken. Tostitch these images, each N^(th) point may be assumed to represent a 0,0, 0 initial coordinates. The entire point cloud may then be rotatedusing the rotation of the nearest fitted pipe section. The distancebetween two successive images N and N+1 may then be assumed to be thedistance between these two points along the path of FIG. 15 . Successiveimages of the pipe interior may then be automatically processed betweencorresponding poses and positions of the video camera.

Finally, FIGS. 16 a through 16 d show a comparison of various methods ofimage stitching of the prior art (FIGS. 16 a, 16 b, 16 c ) against thatobtained using the method of the present invention shown in FIG. 16 d .A clean round copper pipe without any internal surface defects was usedto obtain all of these images. FIG. 16 a shows a panoramic imageobtained from a plurality of individual images of the pipe interior withreconstruction errors on the mesh, which appear as defects, highlightedwithin the three circles and pointed by two arrows. These are artifactsof image processing and are not indicative of actual pipe defects.

FIG. 16 b shows a panoramic image of the same pipe obtained by manualstitching of the images with variable brightness, indicating lightartifacts as seen in the three circles.

FIG. 16 c is a panoramic image of the same pipe obtained using SfMwithout weight adjustment of the images, thus producing defect-likeartifacts seen within the two circles on the right.

FIG. 16 d shows a panoramic combined image of the pipe obtained usingthe present invention with all the weighting and light adjustments asdescribed above. This image has the most uniform lighting, bestsharpness, and least artifacts as compared to all of the previous threeimages.

It is contemplated that any embodiment discussed in this specificationcan be implemented with respect to any method of the invention, and viceversa. It will also be understood that particular embodiments describedherein are shown by way of illustration and not as limitations of theinvention. The principal features of this invention can be employed invarious embodiments without departing from the scope of the invention.Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, numerous equivalents to thespecific procedures described herein. Such equivalents are considered tobe within the scope of this invention and are covered by the claims.

All publications and patent applications mentioned in the specificationare indicative of the level of skill of those skilled in the art towhich this invention pertains. All publications and patent applicationsare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference. Incorporation byreference is limited such that no subject matter is incorporated that iscontrary to the explicit disclosure herein, no claims included in thedocuments are incorporated by reference herein, and any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one,” butit is also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.” The use of the term “or” in the claims isused to mean “and/or” unless explicitly indicated to refer toalternatives only or the alternatives are mutually exclusive, althoughthe disclosure supports a definition that refers to only alternativesand “and/or.” Throughout this application, the term “about” is used toindicate that a value includes the inherent variation of error for thedevice, the method being employed to determine the value, or thevariation that exists among the study subjects.

As used in this specification and claim(s), the words “comprising” (andany form of comprising, such as “comprise” and “comprises”), “having”(and any form of having, such as “have” and “has”), “including” (and anyform of including, such as “includes” and “include”) or “containing”(and any form of containing, such as “contains” and “contain”) areinclusive or open-ended and do not exclude additional, unrecitedelements or method steps. In embodiments of any of the compositions andmethods provided herein, “comprising” may be replaced with “consistingessentially of” or “consisting of”. As used herein, the phrase“consisting essentially of” requires the specified integer(s) or stepsas well as those that do not materially affect the character or functionof the claimed invention. As used herein, the term “consisting” is usedto indicate the presence of the recited integer (e.g., a feature, anelement, a characteristic, a property, a method/process step or alimitation) or group of integers (e.g., feature(s), element(s),characteristic(s), propertie(s), method/process steps or limitation(s))only.

The term “or combinations thereof” as used herein refers to allpermutations and combinations of the listed items preceding the term.For example, “A, B, C, or combinations thereof” is intended to includeat least one of: A, B, C, AB, AC, BC, or ABC, and if order is importantin a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB.Continuing with this example, expressly included are combinations thatcontain repeats of one or more item or term, such as BB, AAA, AB, BBC,AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan willunderstand that typically there is no limit on the number of items orterms in any combination, unless otherwise apparent from the context.

As used herein, words of approximation such as, without limitation,“about”, “substantial” or “substantially” refers to a condition thatwhen so modified is understood to not necessarily be absolute or perfectbut would be considered close enough to those of ordinary skill in theart to warrant designating the condition as being present. The extent towhich the description may vary will depend on how great a change can beinstituted and still have one of ordinary skilled in the art recognizethe modified feature as still having the required characteristics andcapabilities of the unmodified feature. In general, but subject to thepreceding discussion, a numerical value herein that is modified by aword of approximation such as “about” may vary from the stated value byat least ±1, 2, 3, 4, 5, 6, 7, 10, 12, 15, 20 or 25%.

All of the devices and/or methods disclosed and claimed herein can bemade and executed without undue experimentation in light of the presentdisclosure. While the devices and methods of this invention have beendescribed in terms of preferred embodiments, it will be apparent tothose of skill in the art that variations may be applied to the devicesand/or methods and in the steps or in the sequence of steps of themethod described herein without departing from the concept, spirit andscope of the invention. All such similar substitutes and modificationsapparent to those skilled in the art are deemed to be within the spirit,scope and concept of the invention as defined by the appended claims.

What is claimed is:
 1. A video inspection method for an interior surfaceof a pipe, the method comprising the steps of: a. defining geometricalsize and shape of the interior surface of the pipe, b. providing avideoscope sized to fit inside the pipe, c. advancing the videoscopethrough the pipe while acquiring raw images from a video camera of thevideoscope, d. estimating the video camera pose for at least some of theraw images of step (c), e. sequentially building a pipe point cloud, anda 3D textured model of the interior surface of the pipe from the rawimages with adjustments for video camera poses, followed by adjusting ofimage brightness based on a light distribution model and the videocamera pose, wherein the light distribution model is that of a gradualdecrease of lighting from a center of the video camera pose a peripheryof the raw image, f. unwrapping the images from step (e) usingcorresponding video camera poses and the pipe point cloud to createunwrapped images of the interior surface of the pipe, and g. creating apanoramic image of the interior surface of the pipe by stitching theunwrapped images together.
 2. The method as in claim 1, wherein thevideoscope is equipped with only the video camera and illuminatinglights, and does not include any camera centering hardware, laserprojection hardware, or any other sensor.
 3. The method as in claim 1,wherein the pipe is a small bore pipe with an internal diameter or aninternal size characterizing a cross-section of the pipe being 25 mm orsmaller.
 4. The method as in claim 1, wherein in step (d) the estimatingof video camera poses is done by extracting and matching unique featuresfrom consecutive raw images.
 5. The method as in claim 4, wherein saidstep of extracting and matching unique features is performed using aStructure-from-Motion (SfM) technique.
 6. The method as in claim 1,wherein the step of building the pipe point cloud comprising building afirst point cloud from the raw images, followed by building a secondpipe point cloud to replace the first pipe point cloud usingcharacteristics of the pipe extracted from the first point cloud andknown pipe dimensions, whereby reducing defects and discontinuities ofthe 3D textured model caused by insufficient lighting during imageacquisition in step (c).
 7. The method as in claim 6, wherein the stepof building the pipe point cloud further comprises a step of creating avirtual pipe using known pipe dimensions followed by a step of fittingpipe poses onto the virtual pipe to generate the second pipe pointcloud.
 8. The method of claim 7, wherein the step of fitting pipe posesonto the virtual pipe is conducted by minimizing an average of Euclideandistances between the virtual pipe and the first pipe point cloud. 9.The method as in claim 1, wherein the step of unwrapping the raw imagesis performed using Depth-Image-Based-Rendering (DIBR) and ray tracingtechniques.
 10. The method as in claim 9, wherein the step of unwrappingthe raw images further comprises a step of creating an unwrapped imagewith multiple rays projected onto the virtual pipe in front of the videocamera based on a pose thereof and using the second pipe point cloud.11. The method as in claim 10, wherein the step (g) of creating thepanoramic image further comprises a step of assigning a weight factor toat least some of the pixels on at least some of the raw images, wherebycreating unwrapped and weighted images and increasing the sharpness ofthe panoramic image.
 12. The method as in claim 11, wherein the step ofassigning a weight factor is conducted by gradually increasing theweight factor for each pixel from the periphery of the image towards acenter thereof.
 13. The method as in claim 12, wherein said step ofstitching of unwrapped images is conducted with averaging of the pixelsfrom related images with their respective calculated weight factors.